<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script src="./js/vue.js"></script>
    <script src="./js/city.js"></script>
</head>

<body>
    <div id="app">
        <select name="" id="" v-model="pro" @change="city=0,area=0">
            <option :value="index" v-for="(item,index) in citys">{{item.name}}</option>
        </select>
        <select name="" id=""   v-model="city" @change="getCity">
            <option :value="index" v-for="(item,index) in citys[pro].city">{{item.name}}</option>
        </select>
        <select name="" id="">
            <option :value="index" v-for="(item,index) in citys[pro].city[city].area">{{item}}</option>
        </select>
    </div>
</body>
<script>
    const app = new Vue({
        el: "#app",
        data: {
            citys: data,
            pro: 0,
            city: 0,
            area: 0
        },
        methods: {
            getCity() {
                alert(this.city)
            }
        }
    })
</script>

</html>